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Build an LED Photometer 


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Build an LED Photometer 

Written By: Eric Weinhoffer 


Arduino Uno microcontroller. Rev. 3 (1) 

Breadboard jumper wires, or solid core 22AWG wire (1) 


Did you know that, although they're great for emitting light, LEDs are also capable of 
absorbing light? This idea is leveraged in the fantastic Maker Press book, Atmospheric 
Monitoring with Arduino . which goes into depth on using a variety of LEDs to detect light in 
the atmosphere. With a few simple components, you can build a device that's capable of 
detecting sunrises, sunsets, and even haze and water vapor levels in the atmosphere. 

All parts needed for this build are included in the LED Atmospheric Analyzer Kit , except an 
Arduino, USB Cable and jumper wires. 

This project is pulled directly from the Atmospheric Monitoring with Arduino book, and begins 
on Page 51 . 

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Build an LED Photometer 

• Make sure you have all the parts needed to build the photometer. Everything's included in 
the LED Atmospheric Analyzer Kit except an Arduino and jumper wires. 

• If you got a Sparkfun LCD with your order, have no fear! Look for a red bullet point like 
this for specific instructions. 

• If you haven't soldered together your Maker Shield yet, hop on over to the Make Project 
and make it happen! 

• Once your Maker Shield is ready to go, pop it on top of your Arduino and stick the mini 
breadboard onto the empty space of the board. 

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Build an LED Photometer 

• If you haven't done so already, flip 
to Page 37 of the Atmospheric 
Monitoring with Arduino book and 
start measuring the sensitivity of 
your LEDs. This process will help 
you get accurate readings from 
your photometer. 

• Once you've done that, start the 
photometer build by connecting a 
jumper wire from the Maker 
Shield's 5V and GND headers to 
the mini solderless breadboard. 
Use another jumper to set up a 
GND rail on the opposite side of 
the board as well. 

The speaker will give you audio 
feedback when certain events 
occur, like a new maximum reading 
from one of the LEDs. Solder a 
black wire to one of the speaker's 
metal tabs and plug it into the 
rightmost GND rail of the 
breadboard. Solder a red wire to 
the other tab and plug that into D7 
on the Maker Shield. 

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Build an LED Photometer 

• Now it's time to plug in the LCD. Connect the four-pin cable to the LCD breakout board, 
and four jumpers to the other (black) end of the cable. 

• Hook the VCC pin (red) up to the 5V rail on the breadboard, the GND pin (black) up to the 
rightmost GND rail, the white (RX) to D5 on the Maker Shield, and the yellow (TX) to D3 on 
the Maker Shield. 

• If you have the Sparkfun LCD, connect the GND and 5V ports to the Maker Shield in the 
same way (except there's no cable included, so just screw your jumper wires into the 
terminal blocks on the back of the LCD). Connect the RX port of the LCD to D1 (TX) on the 
Maker Shield. 

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Build an LED Photometer 

• Now we can prepare to install the LEDs. All three (Red, Green, and Blue) will use the 
same GND rail on the mini breadboard, but need their own Analog Pins. So, use three 
jumper wires to connect three rows of the breadboard to Analog pins 1 , 2, and 3 of the 
Maker Shield. 

• Now plug in each of the LEDs' short legs into the GND rail. The longer leg of the Red LED 
goes to Analog Pin 1 , the long leg of the Green LED goes to Pin 2, and the long leg of the 
Blue LED goes to Pin 3. 

• And that's it, you're done! You can find some "Getting Started" code for the photometer 
here . 

This document was last generated on 201 2-1 2-20 01 :24:44 AM. 

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